Defining and Classifying Myopia Report

Daniel Ian Flitcroft, MB.BS. D.Phil, IMI Committee Chair

Children's University Hospital, University College Dublin and Dublin Institute of Technology, Ireland

Committee members:

  • Prof. Kyoko Ohno-Matsui
  • Prof. Lawrence Yannuzzi
  • Prof. Jost Jonas
  • Prof. Jugnoo Rahi
  • Prof. Serge Resnikoff
  • Dr. Monica Jong
  • Prof. Mingguang He
  • Prof. Kovin Naidoo
  • Dr. Susan Vitale
Standardized definitions and consistent choice of thresholds are essential elements of evidence-based medicine. It is hoped that these proposals, or derivations from them, will facilitate rigorous, evidence-based approaches to the study and management of myopia.

PURPOSE

We provide a standardized set of terminology, definitions, and thresholds of myopia and its main ocular complications.

METHODS

Critical review of current terminology and choice of myopia thresholds was done to ensure that the proposed standards are appropriate for clinical research purposes, relevant to the underlying biology of myopia, acceptable to researchers in the field, and useful for developing health policy.

RESULTS

We recommend that the many descriptive terms of myopia be consolidated into the following descriptive categories: myopia, secondary myopia, axial myopia, and refractive myopia. To provide a framework for research into myopia prevention, the condition of ‘‘pre-myopia’’ is defined. As a quantitative trait, we recommend that myopia be divided into myopia (i.e., all myopia), low myopia, and high myopia.

The current consensus threshold value for myopia is a spherical equivalent refractive error ≤ -0.50 diopters (D), but this carries significant risks of classification bias. The current consensus threshold value for high myopia is a spherical equivalent refractive error ≤ -6.00 D. ‘‘Pathologic myopia’’ is proposed as the categorical term for the adverse, structural complications of myopia. A clinical classification is proposed to encompass the scope of such structural complications.

CONCLUSIONS

Standardized definitions and consistent choice of thresholds are essential elements of evidence-based medicine. It is hoped that these proposals, or derivations from them, will facilitate rigorous, evidence-based approaches to the study and management of myopia.

Keywords: myopia, myopia classification, myopia definitions, high myopia, myopia thresholds, high myopia, pathologic myopia

Translated versions of IMI clinical summaries are available at myopiainstitute.org

The publication costs of the International Myopia Institute reports were supported by donations from BHVI, Carl Zeiss Vision, CooperVision, Essilor, 
Alcon, and Vision Impact Institute.

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